This new project analyzes the molecular architecture of synapses in the mammalian brain with an initial focus on the postsynaptic density (PSD). Many molecular components of the PSD are known, but the PSD is so large approximately 10 billion Dathat methods had to be developed to understand how its numerous molecular components are organized. A new approach begins by attaching PSDs to glass, labeling them with immunogold, and then freezing and replicating them for electron microscopy. Work to date reveals a lattice-like structure that forms the core of the PSD and labels heavily for PSD-95. Our current focus is on the enzyme CaMKII which is the major protein in forebrain PSDs. During stress, CaMKII forms aggregates in cell bodies and in spines collects on the cytoplasmic surface of the PSD, accounting for much of the thickening that occurs during stress. We have proposed that this ability to aggregate allows it to continue to buffer calmodulin while protecting the neuron from excessive phosphorylation. We are currently investigating the mechanism of CaMKII aggregation as well as what role it may have in normal neuronal function. As the distributions of functional components are determined we plan to develop a macromolecular architecture of the PSD - synapse, PSD, synaptic structure, PSD-95, NR-1, CaMKII, structural biology